Not enough epoxy mixed and degassed.

General Composites Discussions Composites Talk
#1

So here is the situation I found myself in last night. I’m infusing a part with epoxy total of 6 oz. The process is about half done when I realize I dont have enough resin mixed, I’m going to need another couple ounces. So I quickly mix up more and pour it into my supply container going to infusion and finish the infusion. Problem is I didnt have time to degass the resin I added late so I wont know until tomorrow if I have bubbles in the part.

I’m wondering what you all do in a situation like this. Also I am using MTI hose so once resin hits the hose then vacuum is no longer created. If my resin supply ran out before infusion was done could I then add more or is it to late? Of course with experience I hope to judge the amount needed ahead of time.

#2

Depending on the gel time you can close the resin inlet, and degass more resin. If you are in a real hurry do not degas, but pour in the resin slowly. Thats life…

After opening the resin inlet again, it sometimes takes a while before the resin runs again.

#3

Also, as Herman stated, Life is always better if you pre-weigh your cloth dry stack to determine how much resin your actually going to require plus 5-10% for loss in the tubing and consumables etc.

Russian roulette with resin guessing is going to lodge a bullet in your butt sometime ! :wink:

#4

Hi is there a formula to use for calculating how much resin you will need for the infusion, something that’s no complicated.

lastly how long should the degassing process take? or it depends on how much resin you have?

thanks.

#5

I’d rather have a cup of wasted resin than a throw away part… but I’m kinda new at this.

#6

I’ve done some pretty big parts (>15m2) where it is impossible to have enough resin mixed. I use a bucket with the outlet in the bottom, so when the bucket gets low I just pour more in and if it gets too I low clamp the line till I get more mixed.

I don’t bother to degass as it will do that in the bag, air will sit above the peel ply and zip through the transfer media. When I fill the bucket up the bubbles float to the top away from the outlet.

#7

When we were doing a 23 meter boat (2300 kgs / 5000 lbs of resin) we had a sort of inline resin mixing and degassing station, where we were able to mix and degass batches of 130 kgs / 300 lbs.

On calculating the resin needed, you can do that pretty easily in excel, if you know the factors (Vf) but on theis forum there was a chap called jap-something who made a calculation sheet online. Who can bring that threadup?

#8

http://www.compositescentral.com/showthread.php?t=7372&highlight=resin+calculation

#9

Not complicated is the funny part of this if you read the older thread link posted above, few posts back^^. I hate doing math just before I’m butt deep in prep for infusion. Makes me edgy,lol.
I usually just way my dry stack-(prior to bagging)minus the flow media and peelply, and divide that by whatever my target ratio is. Some aim for 60/40, some 70/30-(generalization of course). I’ll then add 5-10% for waste used up in the tubing,peelply and flow media.
I have generally little to no resin waste when done. If its a replicated part I of course map and record all points on a document that remains with each mold…right down to the days ambient temperature,shop temperature, BaroP, mold temp,cycle times,resin temps,laminate schedules-batch #'s and weight etc.

I’ll be breaking in some new molds this weekend and establishing the dry stack schedule. If I get time,I’ll report back how I did the math and the outcomes.